The present invention relates to devices for injecting, infringing, administering, delivering and dispensing substances, and to methods for making and using such devices, as well as to related peripheral, adjunct, complementary, cooperative and auxiliary devices and methods. More particularly, the present invention relates to the sequential application or use of skin penetrators. In the context of the present invention, the expression “skin penetrators” signifies devices that are introduced through the skin into the body from outside the body. For example, these can be cannulas for administering medicaments, probes that are inserted into the skin or into the underlying tissue, or sensors for measuring a physiological parameter, such as glucose sensors.
Elements of such devices are a puncturing part, which pierces the skin, and an indwelling part, which is introduced into a skin opening or channel formed by the puncturing part and remains there. Known designs have a relatively soft cannula, which is made of plastic material and which forms the indwelling part, and a steel cannula, which is provided with a tip and which extends through the plastic cannula, the tip protruding from the front of the plastic cannula. Upon application or in the use of these known designs, the puncturing part and indwelling part are inserted together, after which the steel cannula is withdrawn from the plastic cannula, such that only the plastic cannula remains in the body. The plastic cannula is attached to a line system (in most cases via an adapter, which can also serve as a guide for the steel cannula) to allow liquid to flow in or out through the skin.
Disadvantages of known systems of this kind include the following: the steel cannula has to be removed and disposed of in a separate operating step. If it remains in the body during the wearing period, it is found to be uncomfortable or painful. The geometry of the cutting edge for the tip of the steel cannula must protrude from the plastic cannula and thus increases the overall length by several millimeters. Introducing the steel cannula into the plastic cannula during the manufacture of the system proves difficult if the soft plastic cannula is even just slightly bent. The plastic cannula could then be damaged or destroyed by the tip of the steel cannula.